Absolute basal】 【absolute datum defined by a waterfront location is _set_ to zero the average sea level elevation of the level of the base surface. Dalian, China have adopted, Taku, Yellow Sea, abandoned Yellow River mouth, Wusong, Pearl River and other base surface.
China in 1956 requirements to the Yellow Sea (Qingdao) of the annual mean sea level as a unified base surface, as China's first national height system, which ended in the past elevation of the system complicated the situation. However, calculation of the base surface is based on tide gauge data of Qingdao series (1950 ~ 1956) is shorter and other reasons, the Chinese authorities decided to re-calculated mapping mean sea level the Yellow Sea, tide gauge stations in Qingdao from 1952 to 1979 the basis for calculating tidal data, and then measured by precise leveling in Qingdao, People's Republic of leveling origin, obtained National Height Datum 1985 elevation and the relationship of the Yellow River in 1956 is:
National Height Datum 1985 elevation = 1956 of the Yellow River-0.029m.
National Height Datum 1985, was opened in May 1987, Department of the Yellow River in 1956 shall be repealed simultaneously. 1985 National Height Datum and converted the old height system is shown in Table 4-4. |
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